Dissertation Research: Investigating the role of the maternally-inherited microbiota in dung beetle development and niche construction

生物体以各种有益的方式改变它们的环境。例子包括物理结构的建造，如巢穴，以及加工或储存食物的技术。屎壳郎特别擅长储存食物。雌性把大型动物的粪便滚成一个球，用特殊的微生物（细菌）接种，在里面产卵，然后把它埋在土壤里。这项研究将研究蜣螂母亲沉积的微生物类型，以及它们如何帮助年幼的蜣螂从粪便中获取营养。了解像蜣螂这样的物种如何改变它们的环境，对于了解它们如何缓冲自己免受环境变化的影响可能是至关重要的。本研究也有助于培养一名研究生、指导本科生研究助理和高中生。本研究将利用食粪虫属的幼虫屎壳虫作为一个新系统来研究：(1)生态位构建的发育、生态和进化后果；(2)屎壳虫幼虫主动改变其发育环境（粪球）的机制，特别关注母体遗传的微生物共生体的作用。首先，研究人员将通过实验评估幼虫生态位构建的已知结果（例如，生长增强）在多大程度上可以用粪球中母体遗传的微生物群的存在来解释。其次，研究人员将使用生化技术开始评估微生物群的代谢能力，假设肠道和粪球微生物群可能会分解复杂的大分子（如纤维素），否则这些大分子是幼虫无法消化的。最后，研究人员将对幼虫肠道和粪球进行16S rRNA基因扩增子测序，以表征蜣螂的微生物群，并确定与增强发育结果相关的微生物类群。更广泛地说，这项工作将促进对生态位构建在发育和进化中的原因和后果的理解，并将阐明微生物在生物营养和发育中的重要性。

Organisms change their surroundings in a variety of beneficial ways. Examples include construction of physical structures, such as nests, and techniques to process or store food. Dung beetles are especially skilled at food storage. Females roll dung from large animals into a ball, inoculate it with special microbes (bacteria), lay their eggs in it, and burry it in the soil. This study will examine the types of microbes deposited by the mother and how they help young dung beetles get nutrients from the dung. Understanding how species like dung beetles can modify their environments may be crucial to understanding how they can buffer themselves against environmental changes. This research also contributes to the training of a graduate student and the mentoring of undergraduate research assistants and high school students. This research will use larval dung beetles in the genus Onthophagus as a novel system for investigating (i) the developmental, ecological, and evolutionary consequences of niche construction, and (ii) the mechanisms by which beetle larvae actively modify their developmental environment (a ball of dung), with particular focus on the role of maternally-inherited microbial symbionts. First, the researchers will experimentally assess the degree to which known outcomes of larval niche construction (e.g., enhanced growth) can be explained by the presence of maternally-inherited microbiota in dung balls. Second, the researchers will use a biochemical technique to begin assessing the metabolic capabilities of the microbiota, hypothesizing that the gut and dung ball microbiota may break down complex macromolecules (e.g. cellulose) that are otherwise indigestible by larvae. Finally, the researchers will perform 16S rRNA gene amplicon sequencing on larval guts and dung balls to characterize the dung beetle microbiota and identify those microbial taxa that are associated with enhanced developmental outcomes. More generally, this work will advance understanding of the causes and consequences of niche construction in development and evolution, and will shed light on the importance of microbes in the nutrition and development of organisms.